FAA recognizes RTCA DO-178C and associated technical supplements (July 2013)

The FAA published AC20-115C on July 19, 2013. In this AC, the FAA recognizes RTCA DO-178C, three
associated technical supplements and the 'Software Tool Qualification Considerations' document.

The actual documents that are the subject of this AC are the following RTCA documents:

- DO-178C, Software Considerations in Airborne Systems and Equipment Certification

- DO-330, Software Tool Qualification Considerations, dated December 13, 2011.

- DO-331, Model-Based Development and Verification Supplement to DO178C and DO-278A,

- DO-332, Object-Oriented Technology and Related Techniques Supplement to DO-178C and DO-278A

- DO-333, Formal Methods Supplement to DO-178C and DO-278A

It has been a long awaited recognition since the release of RTCA DO-178C in December 2011. (In terms of
comparison, RTCA DO-178B was endorsed by the FAA only one month after its publication).

Similarly to the previous AC that it replaces, this new AC describes an acceptable means through the use of
DO-178C, but not the only means, to produce software that meets FAA airworthiness regulations.

AC20-115C includes real technical contents in its 12 pages unlike its predecessor AC20-115B that was a
simple one page endorsement of a newly published standard at the time.

Use of the technology supplements

This AC describes when and how the technical supplements should be used. It notes that supplements
cannot be used as stand-alone documents i.e., they have to be used together with DO-178C.

It does include a few specific conditions about the use of these documents particularly of the model-based
development and verification supplement.

It also points out an aspect that may not be obvious to everyone: DO-332 Object-oriented and related
technologies contain requirements that may be applicable even if the applicant is not using object-oriented
techniques. Dynamic memory management would be among these kinds of requirements.

Modification of legacy software

This AC also addresses situations where legacy software i.e., software previously certified to DO-178,
DO-178A or DO-178B is re-used and modified. Using a clear flow chart, the AC describes the approach to
be followed in these situations to determine if you can continue using the legacy certification approach or
if you need to upgrade to a DO-178C type of certification. These guidelines dealing with all these real-life
situations were certainly expected by the industry and regulators and they will be extremely useful to
many aircraft software certification projects.

Finally the AC is also informative about tool qualification and gives guidance to handle scenarios dealing
with the following parameters: legacy tools or new tools, legacy software and version of DO-178 used as a
certification baseline for legacy software. In some situations a tool will have to be qualified with RTCA DO-330
and in some other situations it can be qualified or continue being qualified with DO-178B.

For up to date knowledge on DO-178C and associated documents and your needs dealing with certification
of airborne software or more generally safety-critical, contact the CSL team.